A powerful food industry lobby group says it contacted Assistant Health Minister Fiona Nash to raise concerns about a Government food star rating website the same day it was pulled down.

Senator Nash has come under fire for ordering the Health Department to take down its food rating website hours after it went live.

Her chief of staff, Alastair Furnival, resigned after it was revealed he had a shareholding in a firm that lobbied for junk food companies.

The Food and Grocery Council has been opposed to the star rating system and CEO Gary Dawson says he contacted Senator Nash's office the day the website went live to raise his concerns.

"On the day, yes, we expressed a view that we thought it was premature," he said.

Mr Dawson says he did not ask for it to be taken down.

Senator Nash has told Parliament the website was a draft that was published inadvertently.

On Wednesday, during a grilling from Labor senators, she refused to say if she had offered her resignation to the Prime Minister over Mr Furnival's links to the lobbying firm Australian Public Affairs (APA).

Tony Abbott said: "All the decisions that Senator Nash has made are eminently justifiable and I support them".

Senator Nash maintains there was never a conflict of interest in her office because Mr Furnival had agreed to remove himself from all directorships and was divesting his shareholdings.

"My chief of staff gave a series of undertakings ensuring a strict separation between the business of APA and himself," she has said.

Senator Nash initially told the Senate Mr Furnival had no links to APA, but several hours later she returned to the chamber to say he had a shareholding.

Labor senators have accused Senator Nash of misleading the Senate, something which she has denied.